roughly working

src/main.cpp

@@ -16,28 +16,56 @@ elapsedMillis timeElapsed;
 #define PIN_RESET 2
 #define PIN_CAR1 3
 
+typedef struct {
+  short pin;
+  unsigned int elapsedTime;
+} CarTimer;
+
+#define PIN_CAR_STARTING 3
+#define CAR_COUNT 1
+CarTimer cars[CAR_COUNT];
+
+// buffer for the LCD line
+char buffer[40];
+
 void setup()
 {
 
   Serial.begin(9600);
 
   pinMode(PIN_RESET, INPUT_PULLUP);
-  pinMode(PIN_CAR1, INPUT_PULLUP);
   pinMode(LED_BUILTIN, OUTPUT);
 
+  // initialize each car PIN
+  for(short i=0; i<CAR_COUNT; i++) {
+    cars[i].pin = PIN_CAR_STARTING + i;
+    pinMode(cars[i].pin, INPUT_PULLUP);
+  }
+
   lcd.begin(20, 4);
   lcd.backlight();
 }
 
+void resetCarTimers() {
+  for(short i=0; i<CAR_COUNT; i++) {
+    cars[i].elapsedTime = 0;
+  }
+}
+
+void displayTimers() {
+  lcd.clear();
+  for(short i=0; i<CAR_COUNT; i++) {
+    lcd.setCursor(0,i);
+    sprintf(buffer, "Car %d: %dms", i+1, cars[i].elapsedTime);
+    lcd.print(buffer);
+  }
+}
+
 unsigned int startTime;         // start time in ms
-bool tripped = false;
-
-char buffer[40];
 unsigned int elapsedTime;
-
 bool started = false;
-bool runnning = false;
-unsigned int car1elapsed = 0;
+
+bool allDone;
 
 void loop()
 {
@@ -47,7 +75,7 @@ void loop()
     lcd.setCursor(0,0);
     lcd.print("Ready?");
     started = false;
-    car1elapsed = 0;
+    resetCarTimers();
     digitalWrite(LED_BUILTIN, LOW);
   } else {
     // if we just started, record current millis counter
@@ -59,18 +87,19 @@ void loop()
     // calculate elapsed time in ms
     elapsedTime = timeElapsed - startTime;
 
-    // if car1 finishes record time
-    if (digitalRead(PIN_CAR1) == LOW && car1elapsed == 0) {
-      car1elapsed = elapsedTime;
+    allDone = true;
+    for(short i = 0; i<CAR_COUNT; i++) {
+      if (cars[0].elapsedTime == 0) {
+        if (digitalRead(cars[i].pin) == LOW) {
+          cars[i].elapsedTime = elapsedTime;
+        } else {
+          allDone = false;
+        }
+      }
     }
 
-    if (car1elapsed != 0) {
-      // stop if all cars are complete or threshold reached
-      lcd.clear();
-      lcd.setCursor(0,0);
-      sprintf(buffer, "Car1: %dms", car1elapsed);
-      lcd.print(buffer);
-      digitalWrite(LED_BUILTIN, HIGH);
+    if (allDone) {
+      displayTimers();
     }
 
   }